In an internal combustion engine, the cylinder head is positioned on the top of the engine block. The cylinder head provides upper portions of each combustion chamber, where each upper portion corresponds to one cylinder of the engine block. The cylinder head may house intake valves, exhaust valves, camshafts, rocker arms and pushrods, and numerous other mechanisms as known in the art.
An intake manifold and an exhaust manifold are typically coupled to the cylinder head. The intake manifold is located between the carburetor and cylinder head. In use, the intake manifold supplies an air-fuel mixture through internal intake ports in the cylinder head to each combustion chamber. In multi-port injected engines, the intake manifold holds fuel injectors that supply an air-fuel mixture to each combustion chamber.
The exhaust manifold is typically coupled to the side of the cylinder head opposite the intake manifold (i.e. the “exhaust side”). The exhaust manifold collects exhaust gases exiting from each combustion chamber through internal exhaust ports in the cylinder head and transfers these exhaust gases to an exhaust pipe of an exhaust system. The exhaust manifold has a plurality of primary pipes in fluid communication with a common exhaust pipe. Each primary pipe is coupled to the cylinder head over the outlet of a corresponding exhaust port such that each primary pipe collects exhaust gases exiting a corresponding combustion chamber and transfers them to the exhaust pipe.
The inlet end of each primary pipe is welded to a manifold inlet flange, which is subsequently bolted to the cylinder head. Since exhaust manifolds are generally constructed of cast iron, the inlet flange is relatively heavy and adds a substantial amount of weight to the engine. In addition, welding the primary pipes to the flange is difficult and complicated as it is necessary to provide a weld about the circumference of each pipe. Since there are usually a number of pipes, adjacent pipes interfere with each other during welding. Thus, welding about the entire circumference of each tube is difficult, expensive and time consuming.
Furthermore, once the primary pipes are welded to the flange, a separate machining or smoothing of the flange is required in order to ensure that the cylinder head contacting surface of the flange is smooth and flat, thereby allowing for the secure formation of a sealing attachment of the flange to the cylinder head. The exhaust side of the cylinder head requires similar machining or smoothing in order to provide a corresponding smooth and flat contacting surface of the cylinder head. Since the machining of these materials is difficult and time consuming, the overall cost of producing the engine is higher. Moreover, even with the machining or smoothing of the surfaces, a manifold gasket is required to ensure a good seal between the cylinder head and exhaust manifold. Further, this manifold gasket adds additional weight to the engine, and, over time, the manifold gasket may fail requiring expensive replacement.
Consequently, there exists a significant need for a cylinder head which will provide a reduction in overall engine manufacture time and cost as well as a reduction in engine weight.